Panasonic G5 has a Micro Four Thirds lens mount and currently there are 98 native lenses available for this mount.
Panasonic G5 doesn't have a sensor based image stabilization system but 22 of these lenses already comes with optical image stabilization.
Since Panasonic G5 has a Four Thirds sensor, it has a focal length multiplier of 2× so you have to multiply lenses original focal length with this multiplier to find the Full Frame equivalent focal length of the lens when mounted on G5.
You may also also be interested in these:
Panasonic G5 Lenses with Image Stabilization
Panasonic G5 Lenses with Weather Sealings